Hydrogen peroxide reaction with lophine

Other spectral methods Red chemiluminescence is observed at 635 nm when hydrogen peroxide reacts with hypochlorite ion in alkaline solution. Unfortunately, the reaction is not sensitive enough for application to potable waters however, substances such as luminol or lophine, which give chemiluminescence... 

A number of chemiluminescent reactions may proceed through unstable dioxetane intermediates (12,43). For example, the classical chemiluminescent reactions of lophine [484-47-9] (18), lucigenin [2315-97-7] (20), and transannular peroxide decomposition. Classical chemiluminescence from lophine (18), where R = CgH, is derived from its reaction with oxygen in aqueous alkaline dimethyl sulfoxide or by reaction with hydrogen peroxide and a cooxidant such as sodium hypochlorite or potassium ferricyanide (44). The hydroperoxide (19) has been isolated and independentiy emits light in basic ethanol (45). 

The oxidation reactions of 2,4,5-triphenylimidazole (lophine) have received considerable attention. With chromic acid it gives benzamide and benzanilide, but even more interest has centred on its involvement in the phenomenon of chemiluminescence. Some of this material has been discussed earlier (Sections 4.06.3.6, 4.07.1.2.1 and 4.07.1.2.3). The oxidative decomposition of lophine in the presence of air is accompanied by the emission of light, and it is the excited singlet state of the diaroylarylamidine (12 Scheme 2) which is the light emitter. The radical (46) derived from oxidation of lophine with aqueous ferricyanide and ethanolic KOH forms a hydroperoxide with hydrogen peroxide with consequent luminescence. When 2,4,5-tri- and 1,2,4,5-tetra-phenylimidazoles are oxidized in dilute methanol solution in the presence of methylene blue, the dibenzoylbenzamidine is also formed under circumstances in which hydroperoxides cannot be intermediates (B-76MI40701). 

Characteristics of proposed CL reaction. In the preliminary study, CL intensities of several types of fluorophores were measured after mixing with only aryloxalate and without addition of hydrogen peroxide. DBP derivatives and pyrimidopyrimidine derivatives showed CL, but the CL was not observed with typical fluorophores that are frequently used in conventional PO-CL reactions such as dansyl, benzoxazole, lophine and fluorescein derivatives. Therefore, it is proposed that this CL reaction can detect DBP derivatives selectively in the presence of other fluorophores. 

Similar to luminol and lucigenin, both lophine and gallic acid also react with alkaline hydrogen peroxide to yield chemiluminescence. In all of these reactions, the emission intensity is proportional to transition metal ion catalyst concentration over finite ranges. Table 1 provides an abbreviated comparison of the selectivity and sensitivity available with these systems. 

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